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2D Nanosheets and Their Nanohybrids

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Nanochemistry".

Deadline for manuscript submissions: 30 June 2024 | Viewed by 6773

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Dr. Jin Jia

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Key Laboratory of Spin Electron and Nanomaterials of Anhui Higher Education Institutes, Suzhou University, Suzhou 234000, China
Interests: nanomaterials; synthesis; characterization; catalysis; supercapacitor
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Prof. Dr. Yucheng Lan

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Department of Physics and Engineering Physics, Morgan State University, Baltimore, MD 21251, USA
Interests: renewable energy; photo-/electro-catalysts; nanosensing; mechanical response; electron microscopy; nanomaterials
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Dear Colleagues,

The unique structure of 2D nanosheets and their nanohybrids is what makes them great candidates for energy catalysis. The high surface area and uniformity of nanosheets make them ideal candidates for use in catalysis. Theoretical and experimental studies show that 2D nanosheets are promising materials for enhancing catalytic activity. Nanosheets are characterized by their nanoscale dimensions. They can be manufactured in various forms and shapes. As such, the unique shape and size of these materials allow them to take on different functions within a wide variety of applications such as catalysis. The energy catalyst 2D nanosheets and their nanohybrids are the most promising materials for a wide range of applications in the future.

Furthermore, 2D materials with ultrathin structures and unique physicochemical properties as well as their designed 2D nanohybrids can serve as novel catalytic materials, which play an important role in green, clean, and sustainable technologies with impact features of environmental friendliness, low-carbon, green, and renewable energy.

This Special Issue will cover the latest material discoveries and progress in the energy catalysis of 2D materials. The topics include 2D nanosheets and their nanohybrids, for example, Graphene, MXenes, transition-metal carbide, sulfide, and phosphides. Moreover, 2D catalytic materials are a new class of heterogeneous catalysts in various electrochemical reaction systems, such as oxygen reduction reaction, hydrogen evolution reaction, oxygen evolution reaction, and electrochemical reduction in carbon dioxides. Topics include, but are not limited to:

Hydrogen evolution reaction;
Oxygen evolution reaction;
Oxygen reduction reaction;
Electrochemical reduction in carbon dioxides;
Ammonia synthesis;
Environment Protection and Remediation, Water Treatment;
Modeling and Simulation.

Dr. Jin Jia
Prof. Dr. Yucheng Lan
Guest Editors

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Keywords

2D nanosheets
nanohybrids
graphene
MXenes
transition-metal carbide
sulfide
phosphides
hydrogen evolution reaction
oxygen evolution reaction
oxygen reduction reaction
electrochemical reduction in carbon dioxides
ammonia synthesis

Related Special Issue

Synthesis, Characterization, and Applications of Nanomaterials for Energy Conversion and Storage in Molecules (14 articles)

Published Papers (10 papers)

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Research

15 pages, 4600 KiB

Open AccessArticle

Rhodamine 6G/Transition Metal Dichalcogenide Hybrid Nanoscrolls for Enhanced Optoelectronic Performance

by Huihui Ye, Hailun Tang, Shilong Yu, Yang Yang and Hai Li

Molecules 2024, 29(12), 2799; https://doi.org/10.3390/molecules29122799 - 12 Jun 2024

Viewed by 153

Abstract

The low light absorption efficiency has seriously hindered the application of two-dimensional transition metal dichalcogenide (TMDC) nanosheets in the field of optoelectronic devices. Various approaches have been used to improve the performance of TMDC nanosheets. Preparation of one-dimensional TMDC nanoscrolls in combination with photoactive materials has been a promising method to improve their properties recently. In this work, we report a facile method to enhance the optoelectronic performance of TMDC nanoscrolls by wrapping the photoactive organic dye rhodamine (R6G) into them. After R6G molecules were deposited on monolayer TMDC nanosheets by the solution method, the R6G/MoS₂ nanoscrolls with lengths up to hundreds of microns were prepared in a short time by dropping a mixture of ammonia and ethanol solution on the R6G/MoS₂ nanosheets. The as-obtained R6G/MoS₂ nanoscrolls were well characterized by optical microscopy, atomic force microscopy, Raman spectroscopy, and transmission electron microscopy to prove the encapsulation of R6G. There are multiple type II heterojunction interfaces in the R6G/MoS₂ nanoscrolls, which can promote the generation of photo-induced carriers and the following electron–hole separation. The separated electrons were transported rapidly along the axial direction of the R6G/MoS₂ nanoscrolls, which greatly improves the efficiency of light absorption and photoresponse. Under the irradiation of an incident 405 nm laser, the photoresponsivity, carrier mobility, external quantum efficiency, and detectivity of R6G/MoS₂ nanoscrolls were enhanced to 66.07 A/W, 132.93 cm²V⁻¹s⁻¹, 20,261%, and 1.25 × 10¹² cm·Hz^1/2W⁻¹, which are four orders of magnitude higher than those of monolayer MoS₂ nanosheets. Our work indicates that the R6G/TMDC hybrid nanoscrolls could be promising materials for high-performance optoelectronic devices. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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20 pages, 9524 KiB

Open AccessArticle

First-Principles Investigation of Phosphorus-Doped Graphitic Carbon Nitride as Anchoring Material for the Lithium-Sulfur Battery

by Yuehui Chen, Fengxia Liu, Shuang Wei, Yingkai Xia, Xiaodong Li, Shengnan Liu, Xu Zhang, Shuwei Tang, Ding Shen, Wei Dong and Shaobin Yang

Molecules 2024, 29(12), 2746; https://doi.org/10.3390/molecules29122746 - 9 Jun 2024

Viewed by 249

Abstract

The utilization of lithium–sulfur battery is hindered by various challenges, including the “shuttle effect”, limited sulfur utilization, and the sluggish conversion kinetics of lithium polysulfides (LiPSs). In the present work, a theoretical design for the viability of graphitic carbon nitride (g-C₃N₄) and phosphorus-doping graphitic carbon nitride substrates (P-g-C₃N₄) as promising host materials in a Li-S battery was conducted utilizing first-principles calculations. The PDOS shows that when the P atom is introduced, the 2p of the N atom is affected by the 2p orbital of the P atom, which increases the energy band of phosphorus-doping substrates. The energy bands of P_C and P_i are 0.12 eV and 0.20 eV, respectively. When the lithium polysulfides are adsorbed on four substrates, the overall adsorption energy of P_C is 48–77% higher than that of graphitic carbon nitride, in which the charge transfer of long-chain lithium polysulfides increase by more than 1.5-fold. It is found that there are powerful Li-N bonds between lithium polysulfides and P-g-C₃N₄ substrates. Compared with the graphitic carbon nitride monolayer, the anchoring effect of the LiPSs@P-g-C₃N₄ substrate is enhanced, which is beneficial for inhibiting the shuttle of high-order lithium polysulfides. Furthermore, the catalytic performance of the P-g-C₃N₄ substrate is assessed in terms of the S₈ reduction pathway and the decomposition of Li₂S; the decomposition energy barrier of the P-g-C₃N₄ substrate decrease by 10% to 18%. The calculated results show that P-g-C₃N₄ can promote the reduction of S₈ molecules and Li-S bond cleavage within Li₂S, thus improving the utilization of sulfur-active substances and the ability of rapid reaction kinetics. Therefore, the P-g-C₃N₄ substrates are a promising high-performance lithium-sulfur battery anchoring material. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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14 pages, 4827 KiB

Open AccessArticle

The Preparation of g-C₃N₄/ZnIn₂S₄ Nano-Heterojunctions and Their Enhanced Efficient Photocatalytic Hydrogen Production

by Hubing Li, Yaoting Wang, Song Wang and Xin Xiao

Molecules 2024, 29(11), 2571; https://doi.org/10.3390/molecules29112571 - 30 May 2024

Viewed by 184

Abstract

Hydrogen production technology has triggered a research boom in order to alleviate the problems of environmental pollution and the pressure on non-renewable energy sources. The key factor of this technology is the use of an efficient photocatalyst. g-C₃N₄ is a typical semiconductor photocatalytic material that is non-toxic and environmentally friendly and does not cause any serious harm to human beings. Therefore, it can be applied to drug degradation and the photocatalytic production of H₂. Combined with ZnIn₂S₄, this semiconductor photocatalytic material, with a typical lamellar structure, has become one of the most promising catalysts for research due to its suitable bandgap structure and excellent photoelectric properties. In this study, 10% g-C₃N₄/ZnIn₂S₄ nano-heterojunction composite photocatalytic materials were successfully prepared by compounding ZnIn₂S₄ and g-C₃N₄ semiconductor materials with good visible-light-trapping ability. Under visible light irradiation, the photocatalytic activity of the composites was significantly better than that of pure g-C₃N₄ and ZnIn₂S₄. This is attributed to the formation of a heterojunction structure, which effectively inhibited the recombination of photogenerated carriers through the interfacial contact between the two semiconducting materials, and then improved the separation efficiency of the photogenerated electron–hole pairs, thus enhancing the catalytic activity. In this study, pure g-C₃N₄ and ZnIn₂S₄ were prepared using calcination and hydrothermal methods, and then, the composites were synthesized using ultrasonic and hydrothermal means. The differences in the structure, morphology, and hydrogen production performance of the materials before and after recombination were analyzed in detail using XRD, SEM, and FTIR characterization, which further verified that the 10% g-C₃N₄/ZnIn₂S₄ nano-heterojunction composites possessed excellent photocatalytic activity and stability, providing new possibilities for the optimization and application of photocatalytic hydrogen production technology. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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12 pages, 3506 KiB

Open AccessArticle

Highly Responsive and Self-Powered Photodetector Based on PtSe₂/MoS₂ Heterostructure

by Haoran Li and Zhibin Yang

Molecules 2024, 29(11), 2553; https://doi.org/10.3390/molecules29112553 - 29 May 2024

Viewed by 279

Abstract

In recent years, 2D materials and their heterostructures have started to offer an ideal platform for high-performance photodetection devices. In this work, a highly responsive, self-powered photodetector based on PtSe₂/MoS₂ van der Waals heterostructure is demonstrated. The device achieves a noteworthy wide band spectral response from visible (405 nm) range to the near infrared region (980 nm). The remarkable photoresponsivity and external quantum efficiency up to 4.52 A/W, and 1880% are achieved, respectively, at 405 nm illumination with fast response time of 20 ms. In addition, the photodetector exhibits a decent photoresponsivity of 33.4 mA/W at zero bias, revealing the photodetector works well in the self-driven mode. Our work suggests that a PtSe₂/MoS₂ heterostructure could be a potential candidate for the high-performance photodetection applications. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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12 pages, 7008 KiB

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Nanoscale Evaluation of the Degradation Stability of Black Phosphorus Nanosheets Functionalized with PEG and Glutathione-Stabilized Doxorubicin Drug-Loaded Gold Nanoparticles in Real Functionalized System

by Thisari Maleesha Gunathilaka and Masaru Shimomura

Molecules 2024, 29(8), 1746; https://doi.org/10.3390/molecules29081746 - 12 Apr 2024

Viewed by 561

Abstract

Two-dimensional black phosphorus (2D BP) has attracted significant research interest in the field of biomedical applications due to its unique characteristics, including high biocompatibility, impressive drug-loading efficiency, phototherapeutic ability, and minimal side effects. However, its puckered honeycomb lattice structure with lone-pair electrons of BP leads to higher sensitivity and chemical reactivity towards H₂O and O₂ molecules, resulting in the degradation of the structure with physical and chemical changes. In our study, we synthesize polyethylene glycol (PEG) and glutathione-stabilized doxorubicin drug-assembled Au nanoparticle (Au-GSH-DOX)-functionalized BP nanosheets (BP-PEG@Au-GSH-DOX) with improved degradation stability, biocompatibility, and tumor-targeting ability. Transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy indicate the nanoscale degradation behavior of synthesized nanoconjugates in three different environmental exposure conditions, and the results demonstrate the remarkable nanoscale stability of BP-PEG@Au-GSH-DOX against the degradation of BP, which provides significant interest in employing 2D BP-based nanotherapeutic agents for tumor-targeted cancer phototherapy. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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14 pages, 3762 KiB

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Broadening the Voltage Window of 3D-Printed MXene Micro-Supercapacitors with a Hybridized Electrolyte

by Xin Jiang, Haowen Jia, Xuan Chen, Jiajia Li, Yanling Chen, Jin Jia, Guangzhen Zhao, Lianghao Yu, Guang Zhu and Yuanyuan Zhu

Molecules 2024, 29(6), 1393; https://doi.org/10.3390/molecules29061393 - 20 Mar 2024

Cited by 1 | Viewed by 751

Abstract

The burgeoning demand for miniaturized energy storage devices compatible with the miniaturization trend of electronic technologies necessitates advancements in micro-supercapacitors (MSCs) that promise safety, cost efficiency, and high-speed charging capabilities. However, conventional aqueous MSCs face a significant limitation due to their inherently narrow electrochemical potential window, which restricts their operational voltage and energy density compared to their organic and ionic liquid counterparts. In this study, we introduce an innovative aqueous NaCl/H₂O/EG hybrid gel electrolyte (comprising common salt (NaCl), H₂O, ethylene glycol (EG), and SiO₂) for Ti₃C₂T_x MXene MSCs that substantially widens the voltage window to 1.6 V, a notable improvement over traditional aqueous system. By integrating the hybrid electrolyte with 3D-printed MXene electrodes, we realized MSCs with remarkable areal capacitance (1.51 F cm⁻²) and energy density (675 µWh cm⁻²), significantly surpassing existing benchmarks for aqueous MSCs. The strategic formulation of the hybrid electrolyte—a low-concentration NaCl solution with EG—ensures both economic and environmental viability while enabling enhanced electrochemical performance. Furthermore, the MSCs fabricated via 3D printing technology exhibit exceptional flexibility and are suitable for modular device integration, offering a promising avenue for the development of high-performance, sustainable energy storage devices. This advancement not only provides a tangible solution to the challenge of limited voltage windows in aqueous MXene MSCs but also sets a new precedent for the design of next-generation MSCs that align with the needs of an increasingly microdevice-centric world. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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12 pages, 3265 KiB

Open AccessArticle

In Situ Hybridization Strategy Constructs Heterogeneous Interfaces to Form Electronically Modulated MoS₂/FeS₂ as the Anode for High-Performance Lithium-Ion Storage

by Dazhi Li, Changlong Sun, Zeqing Miao, Kesheng Gao, Zeyang Li, Wei Sun, Shengjing Guan, Xiaofei Qu and Zhenjiang Li

Molecules 2024, 29(6), 1387; https://doi.org/10.3390/molecules29061387 - 20 Mar 2024

Viewed by 586

Abstract

The interfacial effect is important for anodes of transition metal dichalcogenides (TMDs) to achieve superior lithium-ion storage performance. In this paper, a MoS₂/FeS₂ heterojunction is synthesized by a simple hydrothermal reaction to construct the interface effect, and the heterostructure introduces an inherent electric field that accelerates the de-embedding process of lithium ions, improves the electron transfer capability, and effectively mitigates volume expansion. XPS analysis confirms evident chemical interaction between MoS₂ and FeS₂ via an interfacial covalent bond (Mo–S–Fe). This MoS₂/FeS₂ anode shows a distinct interfacial effect for efficient interatomic electron migration. The electrochemical performance demonstrated that the discharge capacity can reach up to 1217.8 mA h g⁻¹ at 0.1 A g⁻¹ after 200 cycles, with a capacity retention rate of 72.9%. After 2000 cycles, the capacity retention is about 61.6% at 1.0 A g⁻¹, and the discharge capacity can still reach 638.9 mA h g⁻¹. Electrochemical kinetic analysis indicated an enhanced pseudocapacitance contribution and that the MoS₂/FeS₂ had sufficient adsorption of lithium ions. This paper therefore argues that this interfacial engineering is an effective solution for designing sulfide-based anodes with good electrochemical properties. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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14 pages, 2866 KiB

Open AccessArticle

Controllable La Deficiency Engineering within Perovskite Oxides for Enhanced Overall Water Splitting

by Xiaohu Xu, Kaiwei Guo and Xinyue Yu

Molecules 2024, 29(6), 1342; https://doi.org/10.3390/molecules29061342 - 18 Mar 2024

Viewed by 732

Abstract

Recently, perovskite (ABO₃) nanomaterials have been widely explored as a class of versatile electrocatalysts for oxygen evolution reactions (OER) due to their remarkable compositional flexibility and structural tunability, but their poor electrical conductivity hinders hydrogen evolution reaction (HER) activity and further limits the large-scale application of perovskite oxide in overall water splitting (OWS). In this study, hollow-nanotube-structure La_xCo_0.4Fe_0.6O_3−δ (x = 1.0, 0.9, and 0.8) perovskites with superior HER/OER activity were synthesized on nickel-iron alloy foam (denoted La_xCoFe/NFF) using hydrothermal with a subsequent calcination strategy. Among them, La_0.9CoFe/NFF not only exhibited extraordinary HER electrocatalytic performance (160.5 mV@10 mA cm⁻² and 241.0 mV@100 mA cm⁻²) and stability (20 h@10 mA cm⁻²), but also displayed significant OER electrocatalytic activity (234.7 mV@10 mA cm⁻² and 296.1 mV@100 mA cm⁻²) and durability (20 h@10 mA cm⁻²), outperforming many recently reported HER/OER perovskite catalysts. The increase in oxygen vacancies caused by the introduction of La deficiency leads to the expansion of the lattice, which greatly accelerates the HER/OER process of La_0.9CoFe/NFF. Additionally, the naturally porous skeleton can prevent catalysts from aggregating as well as delay the corrosion and dissolution of catalysts in the electrolyte under high applied potentials. Furthermore, the assembled two-electrode configuration, utilizing La_0.9CoFe/NFF (cathode and anode) electrodes, only requires a low cell voltage of 1.573 V at 10 mA cm⁻² for robust alkaline OWS, accompanied by remarkable durability over 20 h. This work provides inspiration for the design and preparation of high-performance and stable bifunctional perovskite electrocatalysts for OWS. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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12 pages, 4849 KiB

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Construction of Single-Atom Catalysts for N, O Synergistic Coordination and Application to Electrocatalytic O₂ Reduction

by Jin-Hang Liu, Huixiong Jiang, Bokai Liao, Xiaohua Cao, Langhua Yu and Xiudong Chen

Molecules 2023, 28(21), 7264; https://doi.org/10.3390/molecules28217264 - 25 Oct 2023

Viewed by 1143

Abstract

Replacing expensive platinum oxygen reduction reaction (ORR) catalysts with atomically dispersed single-atom catalysts is an effective way to improve the energy conversion efficiency of fuel cells. Herein, a series of single-atom catalysts, TM-N₂O₂C_x (TM=Sc-Zn) with TM-N₂O₂ active units, were designed, and their catalytic performance for electrocatalytic O₂ reduction was investigated based on density functional theory. The results show that TM-N₂O₂C_x exhibits excellent catalytic activity and stability in acidic media. The eight catalysts (TM=Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) are all 4e⁻ reaction paths, among which Sc-N₂O₂C_x, Ti-N₂O₂C_x, and V-N₂O₂C_x follow dissociative mechanisms and the rest are consistent with associative mechanisms. In particular, Co-N₂O₂C_x and Ni-N₂O₂C_x enable a smooth reduction in O₂ at small overpotentials (0.44 V and 0.49 V, respectively). Furthermore, a linear relationship between the adsorption free energies of the ORR oxygen-containing intermediates was evident, leading to the development of a volcano plot for the purpose of screening exceptional catalysts for ORR. This research will offer a novel strategy for the design and fabrication of exceptionally efficient non-precious metal catalysts on an atomic scale. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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12 pages, 3996 KiB

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Homogeneous Electrochemical Aptasensor for Sensitive Detection of Zearalenone Using Nanocomposite Probe and Silica Nanochannel Film

by Zhongnan Huang, Xuan Luo, Fei Yan and Bo Zhou

Molecules 2023, 28(21), 7241; https://doi.org/10.3390/molecules28217241 - 24 Oct 2023

Cited by 2 | Viewed by 1019

Abstract

Developing rapid and efficient analytical methods is of great importance for food safety Herein, we present a novel homogeneous electrochemical aptasensor for ultrasensitive quantitative determination of zearalenone (ZEN) based on a nanocomposite probe and silica nanochannel film. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and UV–Vis characterization techniques confirm that graphene oxide (GO) bears an aromatic conjugated structure, along with hydroxyl and carboxyl groups, facilitating the subsequent adsorption of cationic redox hexa-ammine-ruthenium (III) (Ru(NH₃)₆³⁺) and anionic ZEN aptamer, to form a Ru(NH3)63+–ZEN aptamer–GO nanocomposite probe in a homogeneous solution. Vertically-ordered mesoporous silica films (VMSF) bearing silanol groups can be simply grown on the solid indium tin oxide (ITO) electrode surface and enable the selective preconcentration of Ru(NH₃)₆³⁺, eventually leading to signal amplification. Since the detachment of Ru(NH₃)₆³⁺ from the GO surface by the recognized ZEN aptamer in the presence of ZEN, more free Ru(NH₃)₆³⁺ is released in solution and produces enhanced redox signals at the VMSF modified ITO electrode, allowing quantitative detection of ZEN. On the basis of the above sensing strategy, the proposed homogeneity, due to the assistance of graphene, as well as of the signal amplification and anti-fouling effects of VMSF, accurate analysis of ZEN can be realized in maize and Chinese chestnut samples. Full article

(This article belongs to the Special Issue 2D Nanosheets and Their Nanohybrids)

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